It is widely known that the flow rate in vessels can be determined by administering a contrast agent and simultaneously scanning the patient and generating computed tomography images for determining the flow rate of the contrast agent in a vessel of the patient. In this process, the patient is scanned a number of times by a rotating the x-ray source through at least 180°, with computed tomography image data being reconstructed from every 180° scan, in which the progress of a contrast agent perfusion in the vessels of the patient can be recognized. The flow rate can be determined based on this recognizable contrast agent propagation in the vessels of the patient.
In this case, it is a substantial problem that the scanning rate of CT systems, in particular of C-arm systems, is relatively slow, with the contrast agent during the scan or during a half rotation of the scan being able to propagate relatively quickly within a vessel, so that the reconstructed CT images do not represent snapshots in which a sharp edge of the propagation of a contrast agent bolus can be recognized.